The present invention relates to methods and compositions for preventing tissue injury, i.e., due to inflammatory activity.
The inflammatory response serves the purpose of eliminating harmful agents from the body. There is a wide range of pathogenic insults that can initiate an inflammatory response including infection, allergens, autoimmune stimuli, immune response to transplanted tissue, noxious chemicals, and toxins, ischemia/reperfusion, hypoxia, mechanical and thermal trauma. Inflammation normally is a very localized action which serves in expulsion, attenuation by dilution, and isolation of the damaging agent and injured tissue. The body""s response becomes an agent of disease when it results in inappropriate injury to host tissues in the process of eliminating the targeted agent, or responding to a traumatic insult.
As examples, inflammation is a component of pathogenesis in several vascular diseases or injuries. Examples include: ischemia/reperfusion injury (N. G. Frangogiannis et al., in Myocardial Ischemia: Mechanisms, Reperfusion, Protection, M. Karmazyn, ed., Birkhuser Verlag (1996) at 236-284; H. S. Sharma et al., Med. of Inflamm., 6, 175 (1987)), atherosclerosis (R. Ross, Nature, 362, 801 (1993)), inflammatory aortic aneurysms (N. Girardi et al., Ann. Thor. Surg., 64, 251 (1997); D. I. Walker et al., Brit. J. Surg., 59, 609 (1972); R. L. Pennell et al., J. Vasc. Surg., 2, 859 (1985)), and restenosis following balloon angioplasty (see, R. Ross cited above). The cells involved with inflammation include leukocytes (i.e., the immune system cells - neutrophils, eosinophils, lymphocytes, monocytes, basophils, macrophages, dendritic cells, and mast cells), the vascular endothelium, vascular smooth muscle cells, fibroblasts, and myocytes.
The release of inflammatory cytokines such as tumor necrosis factor-alpha (TNFxcex1) by leukocytes is a means by which the immune system combats pathogenic invasions, including infections. TNFxcex1 stimulates the expression and activation of adherence factors on leukocytes and endothelial cells, primes neutrophils for an enhanced inflammatory response to secondary stimuli and enhances adherent neutrophil oxidative activity. See, Sharma et al., cited above. In addition, macrophages/dendritic cells act as accessory cells processing antigen for presentation to lymphocytes. The lymphocytes, in turn, become stimulated to act as pro-inflammatory cytotoxic cells.
Generally, cytokines stimulate neutrophils to enhance oxidative (e.g., superoxide and secondary products) and nonoxidative (e.g., myeloperoxidase and other enzymes) inflammatory activity. Inappropriate and over-release of cytokines can produce counterproductive exaggerated pathogenic effects through the release of tissue-damaging oxidative and nonoxidative products (K. G. Tracey et al., J. Exp. Med., 167, 1211 (1988); and D. N. Mxc3xa4annel et al., Rev. Infect. Dis., 9 (suppl. 5), S602-S606 (1987)). For example, TNFxcex1 can induce neutrophils to adhere to the blood vessel wall and then to migrate through the vessel to the site of injury and release their oxidative and non-oxidative inflammatory products.
Although monocytes collect slowly at inflammatory foci, given favorable conditions, the monocytes develop into long-term resident accessory cells and macrophages. Upon stimulation with an inflammation trigger, monocytes/macrophages also produce and secrete an array of cytokines (including TNFxcex1), complement, lipids, reactive oxygen species, proteases and growth factors that remodel tissue and regulate surrounding tissue functions.
For example, inflammatory cytokines have been shown to be pathogenic in: arthritis (C. A. Dinarello, Semin. Immunol., 4, 133 (1992)); ischemia (A. Seekamp et al., Agents-Actions-Supp., 41, 137 (1993)); septic shock (D. N. Mxc3xa4nnel et al., Rev. Infect. Dis., 9 (suppl. 5), S602-S606 (1987)); asthma (N. M. Cembrzynska et al., Am. Rev. Respir. Dis., 147, 291 (1993)); organ transplant rejection (D. K. Imagawa et al., Transplantation, 51, 57 (1991); multiple sclerosis (H. P. Hartung, Ann. Neurol., 33, 591 (1993)); AIDS (T. Matsuyama et al., AIDS, 5, 1405 (1991)); and in alkali-burned eyes (F. Miyamoto et al., Opthalmic Res., 30, 168 (1997)). In addition, superoxide formation in leukocytes has been implicated in promoting replication of the human immunodeficiency virus (HIV) (S. Legrand-Poels et al., AIDS Res. Hum. Retroviruses, 6, 1389 (1990)).
It is well known that adenosine and some analogs of adenosine that nonselectively activate adenosine receptor subtypes decrease neutrophil production of inflammatory oxidative products (B. N. Cronstein et al., Ann. N.Y. Acad. Sci., 451, 291 (1985); P. A. Roberts et al., Biochem. J., 227, 669 (1985); D. J. Schrier et al., J. Immunol., 137, 3284 (1986); B. N. Cronstein et al., Clinical Immunol. and Immunopath., 42, 76 (1987); M. A. Iannone et al., in Topics and Perspective in Adenosine Research, E. Gerlach et al., eds., Springer-Verlag, Berlin, p. 286 (1987); S. T. McGarrity et al., J. Leukocyte Biol., 44, 411421 (1988); J. De La Harpe et al., J. Immunol., 143, 596 (1989); S. T. McGarrity et al., J. Immunol.,142, 1986 (1989); and C. P. Nielson et al., Br. J. Pharnacol., 97, 882 (1989)). For example, adenosine has been shown to inhibit superoxide release from neutrophils stimulated by chemoattractants such as the synthetic mimic of bacterial peptides, f-met-leu-phe (fMLP), and the complement component C5a (B. N. Cronstein et al., J. Immunol., 135, 1366 (1985)). Adenosine can decrease the greatly enhanced oxidative burst of PMN (neutrophil) first primed with TNF-xcex1 and then stimulated by a second stimulus such as f-met-leu-phe (G. W. Sullivan et al., Clin.Res., 41, 172A (1993)). Additionally, it has been reported that adenosine can decrease the rate of HIV replication in a T-cell line (S. Sipka et al., Acta. Biochim. Biopys. Hung., 23, 75 (1988)). However, there is no evidence that in vivo adenosine has anti-inflammatory activity (G. S. Firestein et al., Clin. Res., 41, 170A (1993); and B. N. Cronstein et al., Clin. Res., 41, 244A (1993)).
It has been suggested that there is more than one subtype of adenosine receptor on neutrophils that can have opposite effects on superoxide release (B. N. Cronstein et al., J. Clin. Invest., 85, 1150 (1990)). The existence of A2A receptor on neutrophils was originally demonstrated by Van Calker et al. (D. Van Calker et al., Eur. J. Pharmacology, 206, 285 (1991)).
There has been progressive development of compounds that are more and more potent and/or selective as agonists of A2A adenosine receptors (AR) based on radioligand binding assays and physiological responses. Initially, compounds with little or no selectivity for A2A receptors were developed, such as adenosine itself or 5xe2x80x2-carboxamides of adenosine, such as 5xe2x80x2-N-ethylcarboxamidoadenosine (NECA) (B. N. Cronstein et al., J. Immunol., 135,1366 (1985)). Later, it was shown that addition of 2-alkylamino substituents increased potency and selectivity, e.g., CV1808 and CGS21680 (M. F. Jarvis et al., J. Pharmacol. Exp. Ther., 251, 888 (1989)). 2-Alkoxy-substituted adenosine derivatives such as WRC-0090 are even more potent and selective as agonists at the coronary artery A2A receptor (M. Ueeda et al., J. Med. Chem., 34, 1334 (1991)). The 2-alklylhydrazino adenosine derivatives, e.g., SHA 211 (also called WRC-0474) have also been evaluated as agonists at the coronary artery A2A receptor (K. Niiya et al., J. Med. Chem., 35, 4557 (1992)).
There is one report of the combination of relatively nonspecific adenosine analogs, R-phenylisopropyladenosine (R-PIA) and 2-chloroadenosine (Cl-Ado) with a phosphodiesterase (PDE) inhibitor resulting in a lowering of neutrophil oxidative activity (M. A. lannone et al., Topics and Perspectives in Adenosine Research, E. Garlach et al., eds., Springer-Verlag, Berlin, pp. 286-298 (1987)). However, R-PIA and Cl-Ado analogs are actually more potent activators of A1 adenosine receptors than of A2A adenosine receptors and, thus, are likely to cause side effects due to activation of A1 receptors on cardiac muscle and other tissues causing effects such as xe2x80x9cheart block.xe2x80x9d
R. A. Olsson et al. (U.S. Pat. No. 5,278,150) disclose selective adenosine A2 receptor agonists of the formula: 
wherein Rib is ribosyl, R1 can be H and R2 can be cycloalkyl. The compounds are disclosed to be useful for treating hypertension, atherosclerosis and as vasodilators.
Olsson et al. (U.S. Pat. No. 5,140,015) disclose certain adenosine A2 receptor agonists of formula: 
wherein C(X)BR2 can be CH2OH and R1 can be alkyl- or alkoxyalkyl. The compounds are disclosed to be useful as vasodilators or an antihypertensives.
Linden et al. (U.S. Pat. No. 5,877,180) is based on the discovery that certain inflammatory diseases, such as arthritis and asthma, may be effectively treated by the administration of compounds which are selective agonists of A2A adenosine receptors, preferably in combination with a Type IV phosphodiesterase inhibitor. An embodiment of the Linden et al. invention provides a method for treating inflammatory diseases by administering an effective amount of an A2A adenosine receptor of the following formula: 
wherein R and X are as described in the patent.
In a preferred embodiment, the Linden et al. invention involves the administration of a Type IV phosphodiesterase (PDE) inhibitor in combination with the A2A adenosine receptor agonist. The Type IV phosphodiesterase (PDE) inhibitor includes racemic and optically active 4-(polyalkoxyphenyl)-2-pyrrolidones of the following formula: 
wherein Rxe2x80x2, R18, R19 and X are as disclosed and described in U.S. Pat. No. 4,193,926. Rolipram is an example of a suitable Type IV PDE inhibitor included within the above formula.
G. Cristalli (U.S. Pat. No. 5,593,975) discloses 2-arylethynyl, 2-cycloalkylethynyl or 2-hydroxyalkylethynyl derivatives, wherein the riboside residue is substituted by carboxy amino, or substituted carboxy amino (R3HNC(O)-). 2-Alkynylpurine derivatives have been disclosed in Miyasaka et al. (U.S. Pat. No. 4,956,345), wherein the 2-alkynyl group is substituted with (C3-C16)alkyl. The xe2x80x2975 compounds are disclosed to be vasodilators and to inhibit platelet aggregation, and thus to be useful as anti-ischemic, anti-atherosclerosis and anti-hypertensive agents.
However, a continuing need exists for selective A2 adenosine receptor agonists useful for therapeutic applications, that have reduced side effects.
The present invention comprises compounds and methods of their use for the treatment of inflammatory activity in mammalian tissue. The inflammatory tissue activity can be due to pathological agents or can be due to physical, chemical or thermal trauma, or the trauma of medical procedures, such as organ, tissue or cell transplantation, angioplasty (PCTA), inflammation following ischemia/reperfusion, or grafting. The present compounds comprise a novel class of 2-alkynyladenosine derivatives, substituted at the ethyne position by substituted cycloalkyl moieties. Preferably, the riboside residue is substituted at the 5xe2x80x2-position (xe2x80x9cXxe2x80x9d) by an N-alkyl-(or cycloalkyl)carboxyamino (xe2x80x9caminocarbonylxe2x80x9d) moiety. Thus, the present invention provides a method for inhibiting the inflammatory response in a mammal, such as a human subject, and protecting the tissue subject to the response, by administering an effective amount of one or more compounds of the invention.
The compounds of the invention have the following general formula (I): 
wherein (a) each R is individually hydrogen, C1-C6 alkyl, C3-C7 cycloalkyl, phenyl or phenyl(C1-C3)-alkyl;
(b) X is xe2x80x94CH2OH, xe2x80x94CO2OH, xe2x80x94CO2R2, xe2x80x94OC(O)R2, CH2OC(O)R2 or C(O)NR3R4;
(c) each of R2, R3 and R4 is individually H, C1-6-alkyl; C1-6-alkyl substituted with 1-3 C1-6-alkoxy, C3-C7 cycloalkyl, C1-6-alkylthio, halogen, hydroxy, amino, mono(C1-6-alkyl)amino, di(C1-6-alkyl)amino, or C6-10-aryl, wherein aryl may be substituted with 1-3 halogen, C1-6-alkyl, hydroxy, amino, mono(C1-6-alkyl)amino, or di(C1-6-alkyl)amino; C6-10-aryl; or C6-10-aryl substituted with 1-3 halogen, hydroxy, amino, mono(C1-6-alkyl)amino, di(C1-6-alkyl)amino, or C1-6-alkyl;
(d) Rxe2x80x2 is (X-(Z)-)n[(C3-C10)cycloalkyl]-(Zxe2x80x2)- wherein Z and Zxe2x80x2are individually (C1-C6)alkyl, optionally interrupted by 1-3 S or nonperoxide O, or is absent, and n is 1-3; or a pharmaceutically acceptable salt thereof.
The invention provides a compound of formula I for use in medical therapy, preferably for use in treating or protecting tissue from inflammation such as an inflammatory response, as well as the use of a compound of formula I for the manufacture of a medicament for the treatment of an inflammatory response due to a pathological condition or symptom in a mammal, such as a human, which is associated with inflammation.
Although certain A2A adenosine receptor agonists have been reported to be vasodilators, and thus to be useful to directly treat hypertension, thrombus, atherosclerosis and the like, the tissue-protective activity of the compounds of formula (I) is not suggested by the prior art.
The invention also includes the use of a combination of these compounds with type IV phosphodiesterase inhibitors for synergistic decreases in the inflammatory response of immune cells.
The invention also provides a pharmaceutical composition comprising an effective amount of the compound of formula I, or a pharmaceutically acceptable salt thereof, in combination with a pharmaceutically acceptable diluent or carrier, and optionally, in combination with a Type IV phosphodiesterase (PDE) inhibitor. Preferably, the composition is presented as a unit dosage form.
Additionally, the invention provides a therapeutic method for preventing or treating a pathological condition or symptom in a mammal, such as a human, wherein the activity of A2A adenosine receptors is implicated and agonism of said activity is desired, comprising administering to a mammal in need of such therapy, an effective amount of a compound of formula I, or a pharmaceutically acceptable salt thereof. It is believed that activation of A2A adenosine receptors inhibits inflammation by effecting neutrophils, mast cells, monocytes/macrophages, T-cells and/or eosinophils. Inhibition of these inflammatory cells results in tissue protection following tissue insults.
Among the inflammatory responses that can be treated (including treated prophylactically) with a compound of formula I, optionally with a Type IV PDE inhibitor, are inflammation due to (a) autoimmune stimulation (autoimmune diseases), such as lupus erythematosus, multiple sclerosis, infertility from endometriosis, type I diabetes mellitus including the destruction of pancreatic islets leading to diabetes and the inflammatory consequences of diabetes, including leg ulcers, Crohn""s disease, ulcerative colitis, inflammatory bowel disease, osteoporosis and rheumatoid arthritis;
(b) allergic diseases such as asthma, hay fever, rhinitis, vernal conjunctivitis and other eosinophil-mediated conditions;
(c) skin diseases such as psoriasis, contact dermatitis, eczema, infectious skin ulcers, open wounds, cellulitis;
(d) infectious diseases including sepsis, septic shock, encephalitis, infectious arthritis, endotoxic shock, gram negative shock, Jarisch-Herxheimer reaction, shingles, toxic shock, cerebral malaria, bacterial meningitis, acute respiratory distress syndrome (ARDS), lyme disease, HIV infection, (TNFxcex1-enhanced HIV replication, TNFxcex1 inhibition of reverse transcriptase inhibitor activity);
(e) wasting diseases: cachexia secondary to cancer and HIV;
(f) organ, tissue or cell transplantation (e.g., bone marrow, cornea, kidney, lung, liver, heart, skin, pancreatic islets) including transplant rejection, and graft versus host disease;
(g) adverse effects from drug therapy, including adverse effects from amphotericin B treatment, adverse effects from immunosuppressive therapy, e.g., interleukin-2 treatment, adverse effects from OKT3 treatment, adverse effects from GM-CSF treatment, adverse effects of cyclosporine treatment, and adverse effects of aminoglycoside treatment, stomatitis and mucositis due to immunosuppression;
(h) cardiovascular conditions including circulatory diseases induced or exasperated by an inflammatory response, such as ischemia, atherosclerosis, peripheral vascular disease, restenosis following angioplasty, inflammatory aortic aneurysm, vasculitis, stroke, spinal cord injury, congestive heart failure, hemorrhagic shock, ischemia/reperfusion injury, vasospasm following subarachnoid hemorrhage, vasospasm following cerebrovascular accident, pleuritis, pericarditis, and the cardiovascular complications of diabetes;
(i) dialysis, including pericarditis, due to peritoneal dialysis;
(j) gout; and
(k) chemical or thermal trauma due to burns, acid, alkali and the like.
Of particular interest and efficacy is the use of the present compounds to treat inflammatory responses due to organ, tissue or cell transplantation, i.e., the transplantation of allogeneic or xenogeneic tissue into a mammalian recipient, autoimmune diseases and inflammatory conditions due to circulatory pathologies and the treatment thereof, including angioplasty, stent placement, shunt placement or grafting. Unexpectedly, it was found that administration of one or more compounds of formula (I) was effective after the onset of the inflammatory response, e.g., after the subject was afflicted with the pathology or trauma that initiates the inflammatory response.
The invention also includes a method for measuring the response, or binding a compound of formula I at or to designated A2A adenosine receptor sites comprising said receptors, in vivo or in vitro, with an amount of a compound of formula I effective to bind to said receptors. Tissue or cells comprising ligand bound receptor sites can be used to measure the selectively of test compounds for specific receptor subtypes, the amount of bioactive compound in blood or other physiological fluids, or can be used as a tool to identify potential therapeutic agents for the treatment of diseases or conditions associated with receptor site activation, by contacting said agents with said ligand-receptor complexes, and measuring the extent of displacement of the ligand and/or binding of the agent, or the cellular response to said agent (e.g., cAMP accumulation).